Various uses are known for high-intensity broadband light sources. For example, it is known to use such light sources with chromatic confocal techniques in optical height sensors. In such an optical height sensor, as described in U.S. Patent Application Publication No. 2006/0109483 A1, which is incorporated herein by reference in its entirety, an optical element having axial chromatic aberration, also referred to as axial or longitudinal chromatic dispersion, may be used to focus a broadband light source such that the axial distance to the focus varies with the wavelength. Thus, only one wavelength will be precisely focused on a surface, and the surface height or position relative to the focusing element determines which wavelength is best focused. Upon reflection from the surface, the light is refocused onto a small detector aperture, such as a pinhole or the end of an optical fiber. Upon reflection from a surface and passing back through the optical system to the in/out fiber, only the wavelength that is well focused on the surface is well focused on the fiber. All of the other wavelengths are poorly focused on the fiber, and so will not couple power efficiently into the fiber. Therefore, for the light returned through the fiber, the signal level will be greatest for the wavelength corresponding to the surface height or position of the surface. A spectrometer type detector measures the signal level for each wavelength in order to determine the surface height.
Certain manufacturers refer to practical and compact systems that operate as described above and that are suitable for chromatic confocal ranging in an industrial setting as chromatic point sensors (CPS). A compact chromatically dispersive optical assembly that is used with such systems is referred to as an “optical pen.” The optical pen is connected through the optical fiber to an electronic portion of the CPS, which transmits light through the fiber to be output from the optical pen and provides the spectrometer that detects and analyzes the returned light.
In known implementations, a Xenon arc lamp is used as a high intensity broadband (e.g., white) light source for a CPS having the measurement rate on the order of 30 kHz. A Xenon arc lamp provides broadband light emission that covers the spectral range and, hence, the height measurement range, of a CPS. It is also a high intensity light source with sufficient energy for obtaining a good S/N ratio at the measurement rate of about 30 kHz and the readout time of about 33 μs (=1/30×10−3). However, in practical applications, a Xenon arc lamp exhibits certain undesirable characteristics, such as a less than desirable lifetime and arc spatial stability. A spatially stable, long lifetime light source is desirable in order to minimize any variation in CPS calibration due to changes in the light source spectral emission with arc movement, and also to minimize the downtime of a CPS. Further, many manufactured workpieces include hybrid materials, which have different reflectance characteristics and thus are saturated at different brightnesses. Thus, a CPS light source can preferably be brightness modulated (e.g., from less to more brightness) at a rate equal to or greater than the CPS measurement rate (e.g., 30 kHz) to allow measurement of hybrid materials. Such high rate light modulation is not practical with known Xenon arc lamps. Similar light source deficiencies are also found in association with other instrument applications, such as spectrometers, and the like.
U.S. Patent Application Publication No. 2010/0097779 A1 (the '779 Publication), which is commonly assigned and hereby incorporated herein by reference in its entirety, discloses a high intensity light source wherein a light emitting phosphor or the like is distributed on a movable member, which is moved continuously through a fixed illuminated spot and emitted light output coupling region. The disclosed configurations are superior to Xenon light sources in many respects, and are particularly suitable as high intensity light sources that have a long operating life, that provide high modulation rates, and that efficiently and economically couple light into an optical fiber, among other advantages. Thus, such light sources are well suited for CPS systems such as that outlined above, for example. However, the '779 Publication does not address the issue of phosphor output variations (e.g., at different locations on a phosphor point source element), which may affect the production of an illumination spectrum.
For various applications, improvements in the operation of various aspects of such high intensity light sources (e.g., utilizing light emitting phosphor) would be desirable (e.g., the ability to address phosphor output variations.)